Mixer-settler



July 10, 1956- M. E. WHATLEY MIXER-SETTLER Filed Aug. 5, 1954 WzL United States Fatent 2,754,179 MIXER-SETTLER Marvin Whatley, Oak Ridge, Tenn., assigner to .the United States of America as represented by the United States Atomic Energy Commission Application August 5, 1954, Serial No. 443,165

2 Claims. (Cl. 23--270.5)

This invention relates to improvements in mixersettlers used in liquid-liquid extraction and more particularly to a multi-stage arrangement of mixer-settlers.

An object of the present invention is to provide an improved construction by which control is separately established in each mixer-settler of an entire group for regulation of the interface in that mixer-settler and improved separation of the liquids therein, whereby there is good separation of the liquids throughout all the mixersettlers in spite of changes in densities in the liquids from one mixer-settler to another and in spite of the small difference in density between the two liquids in a mixersettler.

Other objects will appear from the disclosure.

In the drawing:

Fig. 1 is a vertical sectional view taken on the line 1-1 of Fig. 2 and showing a plurality of mixer-settlers constructed and connected to one another in accordance with the principles of the present invention;

Fig. 2 is a plan view of the mixer-settlers shown in Fig. 1;

Fig. 3 is a fragmentary vertical section showing an adjustable weir tube forming part of the present invention;

Fig. 4 is a vertical sectional view of a modified arrangement of mixer-settlers, taken on the line 4-4 of Fig. 5; and

Fig. 5 is a plan view of the mixer-settlers shown in Fig. 4.

In Figs. 1 and 2 there is shown a plurality of mixersettlers arranged side by side in two lines. Each mixersettler comprises a mixing chamber 1i?, a feeding chamber 11 thereover, a weir tube 12, connecting the mixing and feeding chambers, a settling chamber 13, a duct 14 connecting the base of the settling chamber 13 and the base of the feeding chamber 11, and an overow 15 connecting the tops of the settling chamber 13 and an adjacent feeding chamber 11. For better understanding of the relationship of the mixer-settlers to one another reading from left to right in Figs. 1 and 2, the various aforementioned parts thereof are additionally designated by odd numbers (1), (3), (5), (7), etc. if they are in the front row, by even numbers (2), (4), (6), (8), etc. if they are in the rear row. Thus at the left end of the front row in Figs. 1 and 2, the overflow 15(1) connects the settling chamber 13(1) with the feeding chamber 11(3), which is connected with settling chamber 13(3) by the duct 14(3), and at the left end of rear row, the overlow 15(2) connects the settling chamber 13 (2) with the feeding chamber 11(4), which is connected with the settling chamber 13 (4) by the duct 14(4). The parts of the front row are staggered with respect to corresponding parts in the rear row so that a given mixing chamber in one row is opposite a settling chamber 13 in the other row and is directly connected therewith through an opening 16 which constitutes an outlet for the mixing chamber and an inlet for the settling chamber. Thus mixing chamber 10(3) communicates directly with settling chamber 13(2) through opening.16(2) (3), and the mix- 2,754,179 Patented July l0, 1956 ing chamber 10(4), with settling chamber 13(3) through opening 16(3) (4).

Each settling chamber 13 is of uniform width measured in the direction normal to the plane of Fig. 1 and has, when viewed in elevation in Fig. 1, the shape of an inclined oblique parallelogram from which the two acute corners are removed. Thus each settling chamber has an upper inclined wall 17 and a lower inclined wall 18 parallel thereto. Each settling chamber has at its lower end a vertical wall 19 from which the associated duct 14 extends, and at its upper end a vertical wall 20 from which the overflow 15 extends. The vertical walls 19 and 2t) mark the portions of the parallelogram from which the acute corners are removed. Each settling chamber has this shape rather than that of a rectangle or an oblique parallelogram, because for a given area the parallelogram with acute corners removed has a greater horizontal width at the level of the opening 16 between settling and mixing chambers. Since the horizontal dimension of the settling chamber measured normal to the plane of Fig. 1 is constant, the settling chamber when shaped as indicated has a greater area in a horizontal section taken at the opening 16 for a given volume of settling chamber, and thus the area of an interface 21 between the liquids which may extend horizontally across the settling chamber at the level of the opening 16 is greater. Thus there is a greater opportunity for the liquids to separate from one another in the mixing chamber 13.

Each duct 14 is narrower in the horizontal dimension (normal to the plane of Fig. 1) than each feeding chamber 10, mixing chamber 11, and settling chamber 13, which are of generally equal width. Each duct 14 comprises a short horizontal portion 22 leading directly from the lower vertical wall 19 of the settling chamber 13, a long vertical portion 23 leading from the horizontal portion 22, and a portion 24 located at the top of the vertical portion 23 and formed somewhat as a narrow extension of the feeding chamber 11. Each overow 15 is narrower than the settling chamber 13 and the feeding chamber 11 which it connects.

Each mixing chamber 10 is physically connected with the associated feeding chamber 11 by a short tubular section 25 which has its ends secured in the bottom of the feeding chamber and the top of the mixing chamber. The tubular section 25 has an interior screw thread that engages an external screw thread on the Weir tube 12. Rotation of the weir tube raises or lowers it. This may be carried out by a special tool that engages the Weir tube at its upper end, which may have the shape of a regular polygon if the tool is a wrenc Each mixing chamber 10 contains an impeller 26 secured to and supported by the lower end of a shaft 27 which extends through the feeding chamber 11 and the weir tube 12 into the mixing chamber 11i. Each shaft 27 is suitably supported and rotated through means (not shown) associated with the upper end of the shaft. Each opening 16 is toward one side or the other of the associated mixing Ychamber 119 as viewed in Fig. 1 so as to be laterally offset from the shaft 27 and appropriately positioned with respect to the ends of the impeller 26 so that the mixed liuids in the mixing chamber are eiiiciently propelled through the opening 16 to the associated settling chamber 13. For the odd-numbered units (1), (3), (5), etc. the opening 16 is somewhat to the left of the impeller shaft 27 as viewed in Fig. 1, and for the even-numbered units (2), (4), (6), etc. the opening 16 is somewhat to the right of the impeller shaft as viewed in Fig. 1. Thus all the impellers 26 may be rotated in the same direction to move the mixed fluids eficiently to the openings 16, this direction being clockwise as viewed in Fig. 2. As far as each settling chamber 13 is concerned, the associated opening 16 is well spaced from 3 the walls 17 and 18 on a horizontal line and may be equally spaced from these walls, although this is not a requirement,

The mixer-settlers of the present invention are to handle two liquids, one of a relatively high density such as an aqueous solution of a solvent-extractible metal nitrate, suchras cerium nitrate, containing a salting-out agent such as nitric acid, and the other of relatively low density such as a substantially water-immiscible organic solvent such as tributyl phosphate. The invention is suited to the handling of liquids having small dierences in densities. The two liquids are to be repeatedly mixed and separated from one another, and the organic solvent is to extract metal values from the aqueous solution. The heavier liquid, the aqueous solution, upon reaching anyy given settling chamber 13 will separate out at the bottom thereof and thus, starting with the nth unit, follow the path: feeding chamber 11(11), mixing chamber (11), settling chamber 13(n1), duct 14(n-l), feeding chamber 11(11-1), mixing chamber 10(n-l), settling chamber 13(n--2), etc. The lighter liquid, the organic solvent, will separate out at the top of the settling chamber 13(1) and will follow the path: overow 15(1), feeding chamber 11(3), mixing chamber 10(3), settling chamber 13(2), overflow 15(2), feeding chamber 11(4), mixing chamber 10(4), settling chamber 13(3), overflow (3), feeding chamber 11(5), mixing chamber 10(5), settling chamber 13(4), etc. The heavy liquid will move from right to left as viewed in Figs. l and 2, and the light liquid, from left to right. The two liquids will move in the same direction in the Weir tube 12 and the mixing chamber 11 and through the opening 16 into the settling chamber 13. From the opening 16 the liquids move in opposite vertical directions in the settling chamber 13, the duct 14, and the overflow 15.

It has been previously mentioned that the interface 21 in each settling chamber 13 may be at the level of the opening 16 through which the mixed liquids are received in the settling chamber. With the interface at the opening 16 the mixed liquids will have to pass to a minimum extent through the liquids already separated from one another above or below the interface 21. This means a more complete separation in each settling chamber 13 and better extraction, e. g., of metal values, by the organic solvent from the aqueous solution. Locating the interface 21 at the opening 16 is accomplished by maintenance of the upper end of the associated weir tube 12 at the proper level. The heavier liquid in the duct 14 and the feeding chamber 11 should rise to the top of the Weir tube 12 or just above it, and the lighter'liquid coming from the overow 15 should form a shallow layer on the heavier liquid as both liquids flow into the Weir tube 12 at its upper end. If the interface 21is to be at the opening 16, then the column of lighter liquid in the settling chamber 13 extending from the opening 16 to the overflow 15 must be just balanced by the column of heavier liquid extending in the duct 14 and the feeding chamber 11 from the level of the opening 16 to the top of the weir tube 12. The vertical lengths of these columns should be inversely proportional to the densities of the liquids. If a given interface 21 is not at the opening 16, the Weir tube 12 is adjusted vertically to bring the interface to the opening. The structural arrangement of the instant device permits interface control to be dependent upon the dilerence in height of overow 15 and the top of the Weir tube 12. As a result, control of the interface between two liquids having small difference in density is easily accomplished by adjustment of the difference in height through movement of weir tube 12.

It is important to note that with the arrangement of the present invention there is a separate adjustable weir tube 12 for each interface 21, and thus each interface may be controlled separately from the other interfaces. It Will be understood that the various Weir tubes 12 may require different adjustments, because the densities of the liquids may vary absolutely and relatively to one another from one settling chamber 13 to another, depending on how completely the liquids are separated from one another and the extent to which the materials, such as metal values, have been transferred from the aqueous solution to the organic solvent in the various settling chambers 13.

In the modified form of the present invention shown in Figs. 4V and 5, it may be considered that there are separate units placed side by side so as to extend in a row between right and left as viewed in these figures. Alternate units numbered (1), (3), (5), etc. have the mixing and feeding chambers at the bottom and the settling chamber at the top of Fig. 5, and the remaining alternate units numbered (2), (4), (6), etc. have the mixing and feeding chambers at the top and the settling chamber at the bottom of Fig. 5. Each unit has a mixing chamber 30 and a feeding chamber 31 above it and separated therefrom by a horizontal Wall 32 in which a Weir tube 33 is suitably mounted for vertical adjustment so as to provide communication between the feeding and mixing chambers. For example, the Weir tube may be threaded into the horizontal wall. Each unit also has a settling chamber 34 laterally displaced from the feeding and mixing chambersk normally to the plane of Fig. 4, either into it or out of it, depending on whether the unit is odd-numbered or even-numbered. An opening 35 connects the mixing chamber 30 with the settling chamber 34 of the same unit. An irnpeller 36 rotated by and supported from a shaft 37 pumps mixed liquids from the mixing chamber 30 to the associated settling chamber 34 through the opening 35, which is laterally displaced from the shaft 37 as viewed in Fig. 4 to one side or the other, so that all impellers may advance the mixed liquids eiciently through the openings 35 and may rotate in the same direction, which is counterclockwise when viewed as in Fig. 5. A vertical channel is attached to each settling chamber 34 so as to provide a duct 38 for the heavier liquid leading from a lower portion of the settling chamber 34 of one unit to an opening 39 into the feeding chamber 31 of the next highernumbered unit. A notched recess 40 is formed in the contiguous upper edges of the settling chamber of one unit and the feeding chamber of the next lower-numbered unit. The heavier liquid moves through the units from left to right as viewed in Figs. 4 and 5, and the lighter liquid from right to left. The path of the heavier liquid is feeding chamber 31(1), mixing chamber 30(1), settling chamber 34(1), duct 38(1), Y feeding chamber 31(2) etc. The path of the lighter liquid, starting with the nth unit, is settling chamber 34(n), feeding chamber 31(n-l), mixing chamber 30(n1), settling chamber ber 34(n-l), feeding chamber 31(n-2), etc.

An interface 41 between the liquids in each settling chamber 34 should be located at the level of the opening 35 between the mixing and settling chambers, and this is accomplished by maintenance of the upper end of the weir tube 33 in the next higher-numbered unit at the proper level, in the manner of the construction of Figs. 1 and 2.

The significant feature in both constructions is the adjustment of the top of the Weir tube with respect to associated overflow. Such adjustment may also be carried out by making the overow, rather than the Weir tube, adjustable.

It will be understood that the invention is not limited to the specific embodiment disclosed, inasmuch as other embodiments thereof will be readily apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

l. In combination, a rst plurality of settling chambers arranged in a horizontal line in spaced relation to one another, each settling chamber having an inlet port, a

the p rst plurality of mixing chambers arranged in a line in between the settling chambers of the rst plurality, each mixing chamber having an outlet port, a irst plurality at feeding chambers arranged in a line between the settling chambers of the iirst plurality, each feeding chamber being above a mixing chamber of the rst plurality, a first plurality of Weir tubes, one extending from the top of each mixing chamber through the base of the feeding chamber thereabove, a rst plurality of ducts one connecting the base of each feeding chamber with the base of the settling chamber of the first plurality lying to one side of the said feeding chamber, a first plurality ot overows one leading to the said feeding chamber from a region of the upper end of the settling chamber to the other side of the said feeding chamber above the upper end of the Weir tube, a second plurality of settling chambers, a second plurality of mixing chambers, a second plurality of Weir tubes, a second plurality of ducts, and a second plurality of overflows, all members of the second pluralities being arranged and connected to one another in a manner similar to that in which all the members of the iirst pluralities are arranged and connected to one another, the settling chambers of the second plurality being arranged in a horizontal line horizontally oset from that on which the settling chambers of the rst 25 plurality are arranged and being staggered with respect to the settling chambers of the first plurality, the inlets of the settling chambers of the first plurality being at the same level as and being directly connected with the outlets of the mixing chambers of the second plurality, the inlets of the settling chambers of the second plurality being at the same level as and being directly connected with the outlets of the mixing chambers of the rst plurality.

2. In the combination specied in claim 1, each settling chamber being shaped like an oblique inclined parallelogram with the acute corners removed, the overow being connected with the portion from which the acute upper corner is missing, the duct being connected with the portion from which the acute lower corner is missing.

References Cited in the le of this patent UNITED STATES PATENTS Houghton June 22, 1937 Wainwright June 29, 1954 FOREIGN PATENTS Great Britain Aug. 26, 1953 

1. IN COMBINATION, A FIRST PLURALITY OF SETTLING CHAMBERS ARRANGED IN A HORIZONTAL LINE IN SPACED RELATION TO ONE ANOTHER, EACH SETTLING CHAMBER HAVING AN INLET PORT, A FIRST PLURALITY OF MIXING CHAMBERS ARRANGED IN A LINE IN BETWEEN THE SETTLING CHAMBERS OF THE FIRST PLURALITY, EACH MIXING CHAMBER HAVING AN OUTLET PORT, A FIRST PLURALITY OF FEEDING CHAMBERS ARRANGED IN A LINE BETWEEN THE SETTLING CHAMBERS OF THE FIRST PLURALITY, EACH FEEDING CHAMBER BEING ABOVE A MIXING CHAMBER OF THE FIRST PLURALITY, A FIRST PLURALITY OF WEIR TUBES, ONE EXTENDING FROM THE TOP OF EACH MIXING CHAMBER THROUGH THE BASE OF THE FEEDING CHAMBER THEREABOVE, A FIRST PLURALITY OF DUCTS ONE CONNECTING THE BASE OF EACH FEEDING CHAMBER WITH THE BASE OF THE SETTLING CHAMBER OF THE FIRST PLURALITY LYING TO ONE SIDE OF THE SAID FEEDING CHAMBER, A FIRST PLURALITY OF OVERFLOWS ONE LEADING TO THE SAID FEEDING CHAMBER FROM A REGION OF THE UPPER END OF THE SETTLING CHAMBER TO THE OTHER SIDE OF THE SAID FEEDING CHAMBER ABOVE THE UPPER END OF THE WEIR TUBE, A SECOND PLURALITY OF SETTLING CHAMBERS, A SECOND PLURALITY OF MIXING CHAMBERS, A SECOND PLURALITY OF WEIR TUBES, A SECOND PLURALITY OF DUCTS, AND A SECOND PLURALITY OF OVERFLOWS, ALL MEMBERS OF THE SECOND PLURALITIES BEING ARRANGED AND CONNECTED TO ONE ANOTHER IN A MANNER SIMILAR TO THAT IN WHICH ALL THE MEMBERS OF THE FIRST PLURALITIES ARE ARRANGED AND CONNECTED TO ONE ANOTHER, THE SETTLING CHAMBERS OF THE SECOND PLURALITY BEING ARRANGED IN A HORIZONTAL LINE HORIZONTALLY OFFSET FROM THAT ON WHICH THE SETTLING CHAMBERS OF THE FIRST PLURALITY ARE ARRANGED AND BEING STAGGERED WITH RESPECT TO THE SETTLING CHAMBERS OF THE FIRST PLURALITY, THE INLETS OF THE SETTLING CHAMBERS OF THE FIRST PLURALITY BEING AT THE SAME LEVEL AS AND BEING DIRECTLY CONNECTED WITH THE OUTLETS OF THE MIXING CHAMBERS OF THE SECOND PLURALITY, THE INLETS OF THE SETTLING CHAMBERS OF THE SECOND PLURALITY BEING AT THE SAME LEVEL AS AND BEING DIRECTLY CONNECTED WITH THE OUTLETS OF THE MIXING CHAMBERS OF THE FIRST PLURALITY. 